Goodyear Wheel Replacement
It's funny. In the 13 years I've owned my Fly Baby, the one thing
I've continually cussed out is the Goodyear wheels. They're
hard to get off, almost impossible to put back on, and parts
prices are out of sight ($180 for a set of brake linings).
The one GOOD thing I'd say about them is that the brakes weren't
Every time I had to pull them off to grease the bearings, I'd
scream that I was going to junk the damn things and put something
from the 20th century in their place.
Went out to fly a couple of weeks back. I was pulling the plane
out of the hangar, walking backwards, and turning it to point
down the taxiway when my foot brushed something. The
something went "tinkle tinkle tinkle" as it skittered away.
Now, I was on a public taxiway. No reason to think it was
something associated with my airplane. But I stopped and
started scanning the asphalt.
Found a broken piece of a Goodyear brake clip. Gee, now where
could THAT have come from?
From my left wheel, of course. Each wheel has three of
these spring-loaded clips riveted to the wheel to hold the
internal-gear brake disk in place. My left wheel was
missing one. The part I held was just the outer portion
that normally fit into a square slot on the brake disk to hold
the disk in place. Here's a picture of the wheel, with a
screwdriver holding one of the spring clips up:
As it turned out, one of the three clips
was gone entirely, and one of them had the "head" broken off (that was
the piece I stepped on, in the taxiway). It looks like the clip
failure was precipitated by a crack in the wheel rim. Note the
picture below, taken after the wheel was removed. You can see the
"paint shadow" of the clip that's gone, the deformed rivet that used to
hold it in place, and the crack from the rivet hole to the edge of the
wheel I'm guessing the wheel torqued a bit and the cracked area
popped off the clip.
I considered just buying a set of replacement clips, but the fact was,
that crack wasn't going to go away. Goodyear wheels have a fairly
bad reputation for locking up; they lose clips, and the brake disk
twists slightly and jams in the caliper. After thinking about it
a bit, I figured it was time to bite the bullet and replace the system
The biggest issue I had was how much work was involved to substitute
another manufacturer's wheels for the Goodyears. Most planes have
an axle with a big nut at the end. You slide the wheel on, then
tighten the nut until the wheel bearings just start to bind.
In contrast, the Fly Baby uses a rather simple...nay,
primitive....system. A piece of tubing slides over the axle to
set the wheel's distance from the brake plate (more later), then the
wheel goes on, then another piece of tubing slides onto the axle
outboard of the wheel. This tubing has a through-hole drilled in
it that matches a hole drilled through the end of the axle. A
bolt goes through the hole in the tubing through the axle, and a nut
holds the cross-bolt in place. The left side of the figure below
is an exploded view of the system, and the right side shows what it
looks like when it's all assembled.
So...what's wrong? Obviously, the lengths of the two spacer tubes
are critical. If one or the other is too long, the cross-bolt
won't fit through the outer tubing and the axle. If one or the
other tubing is too short, the wheel will be loose...it'll slide in and
out. The stock system, with the end of the axle threaded and a
big nut, gives a lot of adjustability.
If my new wheels were just a little wider or narrower than my old
Goodyears, my spacer tubes wouldn't be the right size. I
ordered some additional tubing to be able to make new spacers if
necessary, but I was a tad worried about the one with the
cross-hole. I'd have to drill a new tube's cross-hole to match
the axle...a bit tough to do.
There's another factor some folks will mention: the wheel
bearings are designed to have some compression on them. On this
system, the bearings are never really tightened in place. The
bearings will move a bit, and wear out quicker.
I don't think the latter is a big issue with a Fly Baby. My plane
had ~480 hours over 25 years on the Goodyears, and there wasn't any
apparent problem with the bearings. I think a Fly Baby just
put THAT much stress on wheel bearings to begin with.
Finally, it's very difficult to retrofit a nut-type system to an
existing Fly Baby. Both ends of a ~5" tube would have to be
threaded...almost impossible to do on the airplane, so the landing gear
would have to be completely disassembled.
(Before going on, you might want to check out my Wheel Selection page to understand
some of the nomenclature.)
My Fly Baby was built around 6-inch wheels, NOT the 4-inch Cub-Type
Goodrich (note rich,
not year) wheels that Pete specifies. If I'd had the Cub-type
wheels, several companies offer conversion kits for them and my
decision process would have been much easier. But I've got 1.5"
axles, which means I need to use 6-inch wheels.
I had two basic criteria for picking the replacement: The ability
to install with a minimum amount of modification, and the desire that
the brakes not be appreciably more powerful than my Goodyears.
Why the last criteria? Because strong brakes and a tailwheel
configuration are a bad combination. Use too much brake at too
high of a speed, and a taildragger flips over onto its back. Not
for me, thenkyew.
In reality, though, there wasn't much I could do about it...it's not
like brake strength is adjustable. The thing to do was to avoid
buying brakes designed for much heavier aircraft.
I received several suggestions for wheels to use, but
I'd had my eye on
Grove wheels for nearly ten
years. Groves are very similar to the common Cleveland brakes
used in aviation...in fact, they're designed to use the some of the
same parts, like the brake pads. Most of the other suggestions
were for, basically, ultralight wheels. My airplane has a fairly
high empty weight, though (805 lbs), so I didn't want to scrimp on the
I had a bit of a problem, though...all the Grove photos
showed that the calipers bolted to a rectangular four-hole pattern, and
I had a three-hole circular pattern on my Fly Baby.
The folks at Grove
put me straight. The bolt holes were all at
the same radius from the middle... the four bolts were just the
rectangular pattern across the middle of a 6-bolt pattern.
They offered to make me a set of caliper plates that had the full
six-bolt pattern. I ended up getting a set of Grove 61-1 wheels
with the custom caliper plates for their list price for the wheels
Got some other parts, as well. I'd gone through the Aircraft
Spruce catalog and bought some Nylaflow brake line and the fittings I
thought I'd need. I also bought new nuts and washers for the AN6
(3/8") bolts and a jug of brake fluid.
First step was to slack off the master turnbuckle, disconnect the
flying wires, and jack up the left side of the plane. With two
broken clips, the brake disk on my old Goodyears was basically free
already, so it took just a couple of minutes to get the wheel off the
Taking the Goodyear brake caliper off took a bit more work. Two
of the three AN6 bolts were easily removed, but the nut on the last one
was in a recess in the cast-aluminum caliper mount. Couldn't get
a wrench on it. Thought I was going to have to pull the axle insert,
but I was able to jam it with a screwdriver sufficiently to hold it
while loosening the head. I disconnected the brake line, and slid
the Goodyear caliper off.
Mounting the Groves
The Grove brake calipers mount to a plate attached to
the axle. The plate has two heavy-duty bushings that fit thick
pins on the caliper. The caliper isn't actually attached, it can slide
a bit, but of course the two brake pads keep the caliper in place.
I slid the Grove caliper plate into place to put the caliper aft.
Unfortunately, it became clear that the caliper wouldn't be able to be
removed normally, once installed in that position...the slanting gear
leg wouldn't let it slide out of the bushings.
Unfortunately, it also appeared that the AN6 bolts used to hold the
Goodyear calipers were too long for the Grove caliper plates. The
Grove plates are flat metal, and the Goodyear units were thick castings.
Fortunately, this is one of the reasons I decided to take Friday off
from work and fiddle with the brakes. My plan was to build a list
of the parts I needed, then make my oft-repeated Saturday trip to the
airplane parts emporium.
As I mentioned in a previous post, my axles aren't threaded.
There's a piece of steel tubing slid over the axle as a stop to set the
inboard position of the wheel, and another piece of tubing with a
transverse hole for a cross-bolt to hold the wheel in place.
The next thing to do was to figure out the right length for a
replacement inner-axle spacer and determine if I could size it to use
the existing tube-with-cross-bolt on the outside or whether I'd need to
drill a new piece of tubing.
I slid the inner spacer on, then positioned the wheel and slid it down
over the axle. I then pushed the cross-drilled tube into place...
...and it was a perfect fit. The Grove wheels were the same
width- between-the-bearings as my Goodyears.
Right at this point, I started getting excited. Bolt the caliper
plates in place, connect up the brake lines, and I'm flying again!
There was an aviation-maintenance facility on the airport, so I grabbed
one of the old plate-mounting bolts to see if they'd have shorter ones
(I needed an AN6-7A). No luck.
I started thinking about driving to the aviation parts emporium now,
instead of Saturday. Unfortunately, the odds were good that I'd
need *more* parts from them, not just the bolts. I hated making
the 40 mile round trip, especially since it was just starting to hit
rush hour and the route I had to take was one of the worst from the
congestion point of view.
So I reluctantly decided to hold off and make a big Saturday run
instead. I stopped by NAPA Aerospace on the way back to the
hangar and bought three 3/8" bolts so I could temporarily install the
plates so I could run the brakes. I deliberately bought only
enough for one side so I wouldn't be tempted to use them on the
To Grade 5 or Not Grade 5
All right: some of you are probably asking: Why not use the Grade 5
bolts? Grade 5 is nominally the same strength as AN!
I'll admit, my mind was kind of swinging that way...until I actually
bought the Grade 5 bolts. They really looked...cheap...in
comparison to the AN hardware. They were threaded all teh way to
the head, instead of having a smooth "grip length" area where the bolt
made contact with the insides of the holes. And shiny coating on
them really looked cheap, in comparison to the cadmium-plated AN bolts
I was used to.
The store did have Grade 8 bolts, which at least were
cadmium-plated. But the thread size was wrong...they were
3/8"-20, instead of 3/8"-24. The AN365 elastic stop nuts wouldn't
work, I'd have to use lock washers instead.
So...reluctantly, I decided to just use the Grade 5s temporarily, and
run up to the aviation parts store on Satuday. Back to the plane
and bolt (temporarily!) the caliper plate into place. Here's the
temporary installation of the caliper plate, using the Grade 5 bolts:
Time to look at how the connect the
Nylaflow tubing to it. It was instantly obvious that the fittings
I'd bought for the Nylaflow tubing wouldn't fit the pipe/flare fitting
on the caliper, either. So I was out of luck, until and unless I
ordered more parts.
Looking at the position of the caliper, though, it appeared to me as if
I could still use the existing aluminum lines. The calipers won't
have to move much, and the nearest attachment point for my existing
metal lines is a good foot or more away. The flex won't be much,
and with a bit of curve in the line to absorb the motion, it probably
wouldn't be a problem.
The airplane parts emporium would have the fittings I'd need. The
existing tubing might work, but I figured I'd buy more tubing there,
just to be on the safe side.
I spotted a buddy working on his RV-7, and stopped by to talk to him
about the Nylaflow fittings. I mentioned that I was considering
just using aluminum again, and he rummaged under his workbench and
found a long coil of brake line...and his flaring tool.
At this point, another friend stopped by. We chatted for a bit,
and I described the work I was doing. I mentioned that I'd be
going to the airplane parts emporium Saturday to get the stuff I needed.
The response: "They ain't open on Saturday, anymore."
A quick phone call confirmed it. They were closing in forty-five
minutes, and it'd be an hour's drive in rush-hour traffic. My RV
buddy offered to fly me there (5-minute flight), but he had been doing
some maintenance and I didn't want him to rush putting the plane back
So, back to the hangar.
I had anticipated needing an hour or two (or more...) to cut the new
spacers and cross-bolt tubing. Not necessary. With tubing,
flaring tool, and brake fluid on hand, the 3/8" bolts were the only
things keeping me from finishing up the work. And I'd probably
end up *ordering* those, waiting several more days for shipping.
By this point, those 3/8" bolts from NAPA Aerospace were looking
*pretty good*. But...but... This was a fairly critical
location. My plane uses only three bolts, instead of four like
most planes seem to. I reluctantly gave up on the installation
and went home to order some bolts.
The Right Parts, and Ready to Go
Once I got the right parts, installation was "sorta" straightforward.
The right-side caliper plate bolted right to the axle plate welded to
the axle, and the caliper slid into place.
However, the left side was a bit tougher. The axle plate was
apparently slightly closer to the gear leg, and once the plate was in
place, there wasn't enough room to snake in the caliper and slide its
shafts into the plate bushings. I shaved some of the gear leg
wood to try give enough room to put it on, but no go.
Just for S&Gs, I tried to slide the caliper in from the *wrong*
way. It wouldn't go!
The three bolts holding the caliper plate to the axle plate had been
reluctant to seat into place; I figured the bolts had just enough of a
mismatch as to torque the caliper plate slightly and misalign the
bushings. So I backed out the bolts, and shaved the axle plate
bolt holes until the bolts would slide in with little resistance.
I slipped the caliper in place before tightening the bolts, and both
sides were ready for their wheels. When it comes time to replace
the inner pad on the left brake, I'll probably have to at least loosen
the mounting bolts, but this shouldn't be that big of a deal.
One thing I considered at this point was painting the new wheels.
They came with a semi-gloss gray finish, and I contemplated painting
them beige to match the airplane. But I got a bit worried about
how they'd look bad if the paint didn't stick. Decided to go with
the gray, and explore putting together a hub cap of some sort.
Bob Grimstead used plastic picnic plates on his plane....
The old tires and tubes were transferred from the Goodyear wheels, and
it was time to pack the new wheel bearings. I've been packing
bearings the same way since I was 16, but with new, fresh bearings, I
decided to give one of those cone thingies a try...you know, the thing
that clamps the bearing between two fairly flat cones and lets you pump
the grease into the middle area.
I don't know if it was me, or the cheap setup I bought. It would
*not* force the grease into the bearing area, it either oozed out at
the top or the bottom. So I ended up doing it the
old-fashioned way. Here's
a shot from an auto page that pretty much sums it up....
With the right wheel in place, all the spacers installed, and the
cross-pin inserted, the wheel was just slightly loose.
Fortunately, a friend had made me a set of steel shims (just big
washers with 1.5" ID) a few years back, and one of those tightened up
The wheels are both probably about 1/8"-3/16" too far inboard; the
shafts on the calipers don't go completely through. I could shave
the outboard spacer (the one with the cross bolt) a bit and either add
shims to the inboard spacer or make a new spacer. But I figure
it's engaged enough, and will actually improve as the brake pads wear.
One thing that was tickling me to death at this point was how EASY it
was to remove and replace a wheel. With the Goodyears, getting
the gear-toothed brake disk fully engaged inside the wheel was a major
hassle...just managing the clips was work enough.
With the new setup, the wheel just moved off and on without the need to
fiddle with things.
As I was bolting the left wheel into place (WHY is it always the one
side???), I noticed a problem. The tire stem was hitting the
through-bolt on every turn of the wheel. The tire had an
elongated cap with a fitting to remove the valve stem. The right
side had just a plain cap, but it appears that the bolt is slightly
more outboard than the left side. Swapping the caps left to right
did the trick.
With the wheels installed it was time to finish up the brakes.
The outboard half of the caliper slipped into the gap between the inner
portion and the tire, and the bolts were quickly snugged up and
I had put a lot of thought into brake lines, and talked with several
local builders. The Goodyear calipers didn't move, hence a solid
aluminum brake line was the best solution. But the Grove calipers
were self-centering, sliding back and forth a bit.
After fiddling with things a bit, I decided to stick with
aluminum. The caliper doesn't move much, and the aluminum brake
line isn't solidly attached to the airframe (floats a bit
already) The big plus is that the position of the Grove brake
port was almost the same as my old Goodyears...I re-used the same brake
With everything connected, it was time to fill the system with fluid.
The standard was on aircraft is to fill the system from low to
high...pump fluid into the caliper from a low point until it and the
actuating cylinder are full. This purges all the air from the
system as it fills and eliminates the need to bleed the brakes.
All it takes is an old pump-type oil can with a rubber hose that fits
the nipple on the bottom of the caliper.
This was again one of the sore points for my old Goodyears. It
didn't *have* nipples on the bottom of the caliper, just a bolt to stop
the hole. Years earlier, I'd had to carve a plastic tube to jam
into the bolt hole to fill the Goodyear brakes. Getting the tube
to seat decently was a problem, and when the brakes were full, I had to
pull the tube away, stick a finger over the hole to stop the fluid from
draining out, then scramble around with my other hand to find the bolt
that plugged the hole. That Dutch Boy routine got old, real
Happily, the Groves came with a modern bleeder screw.
One traditional "fun part" remained...opening the fill
hole in the top of the brake master cylinders to allow air to escape
while the brake system was being filled. There's no access to it
from the cockpit. The only way to get at it was from below, after
removing the traverse inspection panel just behind the firewall.
See the "existing front inspection panel" in the figure.
Since the master cylinders are vertical, the vent screw is on top, and
completely out of sight. Years ago, my Dad tried to impress upon
me that a good mechanic didn't HAVE to see what he was doing. He
wasn't here, so it was up to me.
SOP to remove the plug is to sit with my back against the wheel,
reaching up past the hinge tube for the rudder pedals and unscrew the
vent. One ends up with an arm completely disappeared inside the
fuselage and a vacant expression on one's face while fingertips do the
work; something like a cow veterinarian who dislikes his line of work.
With the left side being the troubled child, I started there.
Feeling around on the top of the cylinder, it felt like it needed an
Allen wrench. A bit of trial and error, and I found the right one.
Cap off, loosen the bleeder screw, slip the hose over the nipple, and
start pumping. When hydraulic fluid starts dripping from the
fuselage, remove the hose and tighten the bleeder. Re-install the
cap, and tuck the Allen wrench into the pocket for removing the cap on
the right side.
Unfortunately, the wrench didn't fit. Feeling around, it seemed
like, perhaps, something had fallen into the recess of the cap. I
tried a variety of ways to clear it, to no avail. Out of
frustration, I tried squeezing the plug and turning it with my
Whoa...did it move, just slightly? Or was it just my finger
I sat, back against the wheel, left arm jammed in the innards, index
finger and thumb burning as I tried to back the plug away. I'm an
engineer, dammit, not a callused-fingered mechanic. It hurt like
hell...but it did apparently keep moving.
And, eventually, it came free. It was set up for a
standard-bladed screwdriver, not an Allen head. Why in the world
were they different?
Anyway, tanked up the left side, reattached the flying wires, tightened
the master turnbuckle, and it was ready to go. Into the
cockpit. Both pedals initially soft, but a bit of pumping brought
them up. The left one was just a bit softer than the right.
Plenty of daylight left. However...geeze, I was a bit creaky and
achey from crawling around the airplane. Plus, it was a bit
windy... if the brakes for some reason didn't work, it would be a real
bear to get it back to the hangar. Finally, I really wanted to
look at it again, carefully, with fresh eyes before flying it. So
I cleaned up and went home.
Finally, I had a chance to try it out. A good
thorough look-over of the wheels and brakes, then roll the plane
out. My plan was to taxi around the airport for a while, then
bring it back to the hangar and re-inspect. The break-in instructions
said to taxi for a while with the brakes dragging and them let them
The weird thing was, in the month since my last flight, they've started
major construction at my home airport. Taxiways are torn up, and
the usual routes didn't really exist any more. So I had to pay a
lot more attention to where I was going; wingtip clearances that were a
given before didn't hold true any more.
Taxi around, dragging the brakes, and performing tight turns to verify
that the wheels wouldn't shift. Back to the hangar.
The left brake was leaking fluid. I tightened the fitting a bit
more, but I could still see it welling up.
Crap. I had everything I needed to build a new brake line, and an
hour later, I had the new one installed and the brake filled with
fluid. The pedal was definitely harder than it had been; it was
about the same as the right, now. There was initially a bit of
seepage, but tightening the fitting seemed to clear it up. Mount
up, take off, shoot some touch and goes, and return to the hangar to
verify things were OK. No leaks. Work complete.
One of my biggest fears was put to rest; the new brakes aren't touchy
or over-powerful. They seem to be about the same power as my
Goodyears, and that was exactly what I was looking for.
I'm very happy with the wheels/brakes, and very happy with the support
given by the Grove
company. The package was complete, and they modified the caliper
plates at no additional cost.
I did weigh the Goodyears after dismounting the tire and tube.
The Goodyear set was about four pounds lighter than the Grove (6 lbs
per side vs. 8 lbs). I suspect the Goodyears are magnesium, which
was an option on the Grove that I decided to forgo.
Looking at the Goodyears, replacement rather than repair seemed like a
good move. The left wheel had one clip missing entirely, and a
second one broken. There was a short crack from the rivet hole of
the missing one to the edge of the wheel, covered with dirt, mostly
covered by the clip, and the remaining portion looking just like the
myriad scratches on the edge of the wheel. Here's a shot after a
There were other signs of distress on the calipers, some gouging, etc.
where the disk went through.
Now that it's all done, the replacement seems like a MARVELOUSLY good
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